[Equest-users] Unexpected Custom SHGC Results

Liam O'Brien obrien_liam at hotmail.com
Sat Jul 14 12:42:20 PDT 2012

Hi Pete,
I don't have a ton of experience with detailed modelling of shades in eQUEST, specifically, but two things that could be at play:
- The claim from the manufacturer sounds like it's not intended to universal in absolute terms. Also, it would be more conservative to reduce the SHGC by 33 percent than 33 percentage points (as you did) if you're going to take this simplified approach. Therefore, it would be closer to SHGC=0.44. Subtle but significant. You could try using software that specializes in window/shade performance like LBNL Window or Parasol to try to characterize the performance of your specific shade-glazing combination- Depending on the operating conditions and construction of the building, there's a chance your results aren't ridiculous. If shades intercept transmitted solar radiation, then a lot of that energy will almost immediately transfer to the air via convection. If you have thermally massive interior surfaces, there's a chance your building could actually perform better without those shades because the air conditioning won't kick in till later. 
Date: Sat, 14 Jul 2012 11:51:02 -0700
From: pbaumstark at sbcglobal.net
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Unexpected Custom SHGC Results


I have an "L" shaped building with the point of the "L" facing North.  The inside of the "L" has both NE and NW surfaces, that include a high amount of glass, which heats up the perimeter building spaces considerably during the summer.  Glazing is single pane tinted.

The customer wants to install some Verisol SilverScreen shades in these windows.  According to the manufacturer, the SHGC will reduce by about 33%.  I modeled in eQUEST, window properties in these windows to have an SHGC of 0.67 and ran an EEM reducing SHGC to 0.34, and got an increase in cooling load and fan load year round, even in the summer months.

Am I seeing this wrong?  I can't figure out how I could possible get results like this?

Thank you,
San Jose, CA

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